Which of these was the greatest challenge to the Byzantine Empire from the east?

Question

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Persia, particularly the Sassanian Empire, posed the greatest challenge to the Byzantine Empire from the east. The two empires were frequently in conflict over territory and religion, and this conflict ultimately weakened both empires and paved the way for the Arab conquests of the seventh century. The Lombards and Visigoths were Germanic tribes that posed a threat to the Byzantines in the west, while the Huns were a Central Asian nomadic group that challenged the Eastern Roman Empire in the fourth and fifth centuries but ultimately did not pose a long-term threat like Persia did.

Which of These Was the Greatest Challenge to the Byzantine